The shoulder joint has the largest range of motion of any joint in the human body. It is a ball-and-socket joint having three bones: a shoulder blade (scapula), a collarbone (clavicle), and an upper arm bone (humerus). A rounded head of the upper arm bone (humeral head) fits into a shallow socket in the shoulder blade called a glenoid. The humeral head is usually much larger than the glenoid, and together they have little inherent stability. The shoulder joint is thus prone to instability and dislocation. A soft fibrous tissue rim called a labrum surrounds the glenoid to form a cup for the humeral head to move within the glenoid. The labrum thus helps maintain stability of the shoulder, while allowing for a very wide range of motion. When the labrum of the shoulder joint is damaged, the stability of the shoulder joint is compromised, leading to subluxation and dislocation of the joint. Recurrent dislocations may cause damage to the bones of the joint—the humeral head and the glenoid. In particular, damage to the anterior-inferior part of the glenoid will cause a decrease in the area of contact with the humeral head.
Surgical procedures intended to address the shoulder instability are typically divided into soft tissue and bony procedures. Surgical reconstruction targeting the shoulder joint's soft tissues (which typically involves labral repairs) can be adequate to address certain shoulder instability problems. However, in cases where significant bone deficiency is present (e.g., when greater than 20% of the glenoid's surface area is missing), addressing only the soft tissue issues is typically not sufficient. Bone deficiency can result from trauma, overuse, congenital deformity, or recurrent dislocation.
Reestablishment of shoulder stability requires recognition and treatment of bone defects. When bone deficiencies or lesions reach certain dimensions, reconstruction of these deficits is typically performed using a bone graft. Although existing techniques have been used with some success, the bone graft may not be properly aligned with the glenoid or other bone structure being reconstructed. In particular, when the bone to be reconstructed is being prepared for receiving the graft, it may be challenging to identify proper locations for attachment elements (e.g., screws) that are to be inserted into the bone when the graft is attached thereto.
Accordingly, there is a need for improved techniques and devices for preparing a bone for a surgical procedure, such as a procedure involving use of a bone graft.